1. Field of the Invention
The present invention relates to the casing of an engine provided with a crankshaft. A shift input shaft and a shift output shaft are provided with a clutch mounted at one end of the shift input shaft and a primary reduction gear that reduces the rotational speed of the crankshaft and transmits it to the clutch, which are arranged mutually in parallel. In more detail, the invention relates to a casing composed of a crankshaft, a crankcase supporting a shift input shaft and a shift output shaft, a crankcase side cover the inner end of which is joined to one side end of the crankcase and which covers a primary reduction gear and a clutch cover which is joined to the outer end of the crankcase side cover and which forms a clutch chamber for housing a clutch together with the side cover.
2. Description of Background Art
Such a casing of an engine is already known as disclosed in Japanese published unexamined patent application No. Hei 6-48346 for example.
Heretofore, in such a casing of an engine, as the internal wall of a crankcase side cover is extended opposite to a crankcase, the crankcase side cover is of a large-size, as a result, the weight of the crankcase side cover is increased, the inside diameter on the side of a clutch enclosure of the joined faces of the crankcase and the crankcase side cover is larger than the outside diameter of a clutch and the area of each joined face is increased.